|Apr 30, 2012, 09:47 AM|
Joined Nov 2009
This information is good.
What would also help is a methodology to work out raw size of the motor, size of the battery kv rating, weight, size of the prop, and bite of the prop. Rules of thumb in these areas are very useful.
The methodology should include figuring out the raw size of the space in the plane for the power system, the raw weight that the plane could carry, and the relationship between kv and the voltage of the battery.
Most of the postings that I see say "use a motor calculator", which does not teach these basic rules of thumb.
|Jun 06, 2012, 10:38 AM|
Joined Mar 2012
Receiver Power Source
Hi: I'm currently buying some of the tools for RC Flight, I already have a transmitter and some other stuff. I'm not too overly impressed with NiCad since Lipo offers so much better service, but when I bought a Futaba package, it came with a NiCad Battery. Can I plug a lipo batt into a Futaba receiver and have it work?? I have worked as qn Electrician / Technician for years, this situation shouldn't be rocket science, but I'm not totally sure how to proceed. I'm still waiting on a bunch of parts to arrive via mail order. I call myself Zashma, I'm not even sure where this reply will be posted. Maybe someone could send a private message. If so, that would be heplful. Thank you.
|Jun 06, 2012, 05:47 PM|
|Jun 07, 2012, 09:19 AM|
Joined Mar 2012
|Aug 08, 2012, 10:25 PM|
United States, SC, Pelzer
Joined May 2012
I've been looking for the answer to this question in this thread and the noob thread. I thought for sure I saw it somewhere but can't find it.
What does the "s" designation indicate when referring to batteries, i.e. 3s, 5s, 12s, etc. I assume it is shorthand for the number of cells in the battery pack?
|Aug 08, 2012, 10:35 PM|
Joined Apr 2003
Yes, it is noting the number of (series) cells in the pack. It is responsible for the voltage of the pack.
Your examples are 11.1 , 18.5 , and 44.4 volts. (LIPO example only)
|Aug 17, 2012, 12:20 AM|
Not long after I got into the hobby I encountered this same problem (how to choose motor, gearbox, propeller, and battery for a model). At first I tried rules of thumb (like the ubiquitous watts/lb "rules" you'll find all over the Internet). And I found the rules of thumb simply didn't work very well for many models.
After I found out the rules of thumb were useless, I spent quite a long time trying to figure enough of the basic physics of the problem to develop a usable solution. I got there in the end, but, sure enough, the details were too complicated to convert into rules of thumb.
So I ended up writing my own software to do the work. The software is called WebOCalc, it's free, and there are several threads about it scattered here on RCG.
If you tell WebOCalc a few basic things - approximately how much your model weighs, how big its wing is, and what sort of performance you're looking for - the program will take it from there and help you find a suitable motor, propeller, and battery for your model. It will also give you some ballpark predictions about the way the model will fly if you use those components.
WebOCalc, by the way, is not a motor calculator per se. Motor calculators tell you how motor X and propeller Y and battery Z work together, but don't tell you how that combo will actually fly your model. WebOCalc, on the other hand, tells you what motor, battery, and propeller will make your model fly the way you want it to fly - which is what we actually want to know!
Back in 2009 RCG member NoFlyZone wrote up a very nice tutorial on how to use WebOCalc, and it should make things easy for most people:
|Sep 15, 2012, 04:22 AM|
Check out this pretty awesome free online calculator that I found while searching for books on model aviation:
The calculator is on the left side of the page. Although I haven't tried all the functions, it seems like it can do a heck of a lot. Below the calculator hot spot is another hot spot for tutorials. I haven't had a chance to review them, but they look informative.
Just thought I would share that with you guys who are looking for something to help you with your electronic setups.
After stumbling across that and seeing what Carlos does for a living, I suspect this calulator should be a very useful tool.
|Nov 10, 2012, 09:12 AM|
Nederland, Noord-Holland, Krommenie
Joined Nov 2010
Are All Watts Created Equal? or Why Is Bigger Better?
Firstly I'd like to thank Chris, Beagle and all others for this treasure trove of information. This thread has really improved my understanding of electric drive systems. Unfortunately the more I learn, the better I understand that I really still don't have a clue.
So here's the story:
I have 2 Warbirds, a Multiplex DogFigter and a Durafly 1100mm P-51. I'm very happy with the way the Dog flies and wanted to endow the Pony with similar power characteristics. To that end I've tried various set-ups and finally settled for the consensus solution. Though I'm perfectly happy with the results, I'm unclear on why it is better than a similar set-up which I devised myself.
A power meter remains on my wishlist
All batteries are simple Turnigy 2200mAh 3S and 4S, 25C
Personally I run a 10x6 folding prop. Flight times is 8 minutes @ 33%+ throttle.
The stock Mustang (3S)
Sports a 10 inch 4-bladed prop
The stock Mustang (4S)
At this point I still ran the stock prop which yielded great performance, but short flight times
OK, this is where I lost the plot:
Playing around with Web0Calc I decided to try a smaller prop and higher kV motor.
The idea was to achieve the same great performance with longer flight times.
OS Brushless 3820-1200kV (4S)
Here I went with the recommended 8x6 prop and HobbyWing 40A ESC
While the numbers are identical to the previous setup, the flight characteristics were dramatically different.
More "tractor" than "sports car".
Flight times are brilliant though @ 10+ minutes.
So I went for the consensus solution: Stock motor on 4S with a 11x10 prop (also recommended by Web0Calc). Performance seems similar to the stock 4 blader, but with improved fight duration. Problem solved!
Now I just wonder why the last two charts predict such similar performance, but fly so vastly different? I can only deduce that a Watt isn't simply a Watt and that RPMs must figure into the equation. Beagle loves big props and I'm starting to develop a preference for them too, though I'm not sure why
PS -> It would be great if we could also run Web0Calc in reverse, entering the airframe, motor and prop numbers, with speed and thrust predictions as result.
|Nov 21, 2012, 02:32 PM|
United States, OR, Hillsboro
Joined Nov 2012
battery comparison Help
I went from a Sugar High to a rapid Sugar Low of major information regarding this "Power System" Thread.
Looks like I need some food to help digest the simplicities of being a newbie to finding a second battery on my own. I know it's easy to just go to my local hobby shop and get exactly what I need. However I need to learn what is good and bad within my internet search and getting the relative knowledge from you folks.
I have a E-flite LiPo battery 3S 11.1V 3200mAh (35.5Wh) 15C with 48A maximum discharge.
I talk with the a guy at the hobby shop and said I could run a similar 3300mAh battery... OK Great!
In looking into my search I found this;
Even if I calculate the numbers: 15c x 3200mAh /1000 = 48A max output as needed and says on the battery.
So if I calculate the above added link above: 30c x 3300mAh /1000 = 99 max output.
So I guess my question is... ( I do need to read more of this thread, just feeling a little over loaded at this point)
What are the differences with 15c and 30c (I'm, going to kick myself for this one I now it!!!) So laugh with me.
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